1. Field of the Invention
The present invention relates to an ink jet aqueous ink, an ink jet recording method, an ink cartridge and an ink jet recording apparatus. More particularly, the present invention relates to a coloring material dispersion type aqueous ink showing a high ink ejection stability and a good color developability of a printed image and being suitable for ink jet recording, as well as a ink jet recording method using such an ink, an ink cartridge and an ink jet recording apparatus.
2. Description of the Related Art
While known popular ink jet inks are mostly aqueous inks using water-soluble coloring materials, water-insoluble coloring materials such as pigments that are excellent in terms of fastness of printed images such as water fastness and light fastness have been attracting attention. However, because water-insoluble coloring materials do not dissolve in water as a matter of course, they are generally used as coloring materials of non-aqueous inks. Japanese Patent Publication No. S53-3408 proposes a non-aqueous ink prepared by adding anonionic surface active agent such as cholesterin, lanosterin, agnosterin and lanopalmitic acid. However, a number of restrictions are posed on nonionic inks from the viewpoint of odor, health and safety when they are used as ink jet inks, because some organic solvent has to be used with them. In other words, such inks should be carefully handled. Thus, there is a demand for aqueous inks containing water-insoluble coloring materials. When a water-insoluble coloring material is used as a coloring material in aqueous inks, it is necessary to add a dispersing agent typically selected from polymeric compounds and surface active agents to produce a coloring material dispersion type aqueous ink where a water-insoluble coloring material is uniformly dispersed in an aqueous medium.
For the purpose of using such coloring material dispersion type aqueous ink for ink jet recording, attempts have been made to provide the water-insoluble coloring material in the ink with a functional feature of aggregation and that of turning into water-insoluble in order to improve the fixation and the water fastness of the ink on paper. On the other hand, as a result of providing the water-insoluble coloring material with such functional features, the dispersion stability of the water-insoluble coloring material is reduced in the ink to give rise to problems including that the water-insoluble coloring material tends to aggregate during storage to give rise to density unevenness and precipitation and that the ink is dried at the nozzle tip of an ink jet apparatus to clog the nozzle tip to reduce the ejection stability of the ink. Additionally, when printing an image, the water-insoluble coloring material can easily aggregate on the surface of the recording material so that the color saturation is remarkably degraded due to light scattered by aggregated particles to by turn degrade the color developability.
Japanese Patent Application Laid-Open No. H06-107991 proposes an ink containing polyoxyethylene alkylether to dissolve the above problems. However, the proposed ink cannot satisfactorily improve the ejection characteristics of ink.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.